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  • Fluorinated interphases
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Qiang Zhang

    Fluorinated interphases Fluorinated interphases, Published online: 16 July 2018; doi:10.1038/s41565-018-0187-y Fluorine-rich layers on both anode and cathode protect the electrodes and provide rechargeable lithium metal batteries with high energy density and intrinsic safety.

    更新日期:2018-07-18
  • Dissipative adaptation in driven self-assembly leading to self-dividing fibrils
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Esra te Brinke, Joost Groen, Andreas Herrmann, Hans A. Heus, Germán Rivas, Evan Spruijt, Wilhelm T. S. Huck

    Out-of-equilibrium self-assembly of proteins such as actin and tubulin is a key regulatory process controlling cell shape, motion and division. The design of functional nanosystems based on dissipative self-assembly has proven to be remarkably difficult due to a complete lack of control over the spatial and temporal characteristics of the assembly process. Here, we show the dissipative self-assembly of FtsZ protein (a bacterial homologue of tubulin) within coacervate droplets. More specifically, we show how such barrier-free compartments govern the local availability of the energy-rich building block guanosine triphosphate, yielding highly dynamic fibrils. The increased flux of FtsZ monomers at the tips of the fibrils results in localized FtsZ assembly, elongation of the coacervate compartments, followed by division of the fibrils into two. We rationalize the directional growth and division of the fibrils using dissipative reaction–diffusion kinetics and capillary action of the filaments as main inputs. The principle presented here, in which open compartments are used to modulate the rates of dissipative self-assembly by restricting the absorption of energy from the environment, may provide a general route to dissipatively adapting nanosystems exhibiting life-like behaviour.

    更新日期:2018-07-18
  • A quantum-dot heat engine operating close to the thermodynamic efficiency limits
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Martin Josefsson, Artis Svilans, Adam M. Burke, Eric A. Hoffmann, Sofia Fahlvik, Claes Thelander, Martin Leijnse, Heiner Linke

    Cyclical heat engines are a paradigm of classical thermodynamics, but are impractical for miniaturization because they rely on moving parts. A more recent concept is particle-exchange (PE) heat engines, which uses energy filtering to control a thermally driven particle flow between two heat reservoirs1,2. As they do not require moving parts and can be realized in solid-state materials, they are suitable for low-power applications and miniaturization. It was predicted that PE engines could reach the same thermodynamically ideal efficiency limits as those accessible to cyclical engines3,4,5,6, but this prediction has not been verified experimentally. Here, we demonstrate a PE heat engine based on a quantum dot (QD) embedded into a semiconductor nanowire. We directly measure the engine’s steady-state electric power output and combine it with the calculated electronic heat flow to determine the electronic efficiency η. We find that at the maximum power conditions, η is in agreement with the Curzon–Ahlborn efficiency6,7,8,9 and that the overall maximum η is in excess of 70% of the Carnot efficiency while maintaining a finite power output. Our results demonstrate that thermoelectric power conversion can, in principle, be achieved close to the thermodynamic limits, with direct relevance for future hot-carrier photovoltaics10, on-chip coolers or energy harvesters for quantum technologies.

    更新日期:2018-07-18
  • Non-flammable electrolyte enables Li-metal batteries with aggressive cathode chemistries
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Xiulin Fan, Long Chen, Oleg Borodin, Xiao Ji, Ji Chen, Singyuk Hou, Tao Deng, Jing Zheng, Chongyin Yang, Sz-Chian Liou, Khalil Amine, Kang Xu, Chunsheng Wang

    Rechargeable Li-metal batteries using high-voltage cathodes can deliver the highest possible energy densities among all electrochemistries. However, the notorious reactivity of metallic lithium as well as the catalytic nature of high-voltage cathode materials largely prevents their practical application. Here, we report a non-flammable fluorinated electrolyte that supports the most aggressive and high-voltage cathodes in a Li-metal battery. Our battery shows high cycling stability, as evidenced by the efficiencies for Li-metal plating/stripping (99.2%) for a 5 V cathode LiCoPO4 (~99.81%) and a Ni-rich LiNi0.8Mn0.1Co0.1O2 cathode (~99.93%). At a loading of 2.0 mAh cm−2, our full cells retain ~93% of their original capacities after 1,000 cycles. Surface analyses and quantum chemistry calculations show that stabilization of these aggressive chemistries at extreme potentials is due to the formation of a several-nanometre-thick fluorinated interphase.

    更新日期:2018-07-18
  • Surface chemistry and buried interfaces in all-inorganic nanocrystalline solids
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Emilio Scalise, Vishwas Srivastava, Eric Janke, Dmitri Talapin, Giulia Galli, Stefan Wippermann

    Semiconducting nanomaterials synthesized using wet chemical techniques play an important role in emerging optoelectronic and photonic technologies. Controlling the surface chemistry of the nano building blocks and their interfaces with ligands is one of the outstanding challenges for the rational design of these systems. We present an integrated theoretical and experimental approach to characterize, at the atomistic level, buried interfaces in solids of InAs nanoparticles capped with Sn2S64– ligands. These prototypical nanocomposites are known for their promising transport properties and unusual negative photoconductivity. We found that inorganic ligands dissociate on InAs to form a surface passivation layer. A nanocomposite with unique electronic and transport properties is formed, that exhibits type II heterojunctions favourable for exciton dissociation. We identified how the matrix density, sulfur content and specific defects may be designed to attain desirable electronic and transport properties, and we explain the origin of the measured negative photoconductivity of the nanocrystalline solids.

    更新日期:2018-07-18
  • High Purcell factor generation of indistinguishable on-chip single photons
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Feng Liu, Alistair J. Brash, John O’Hara, Luis M. P. P. Martins, Catherine L. Phillips, Rikki J. Coles, Benjamin Royall, Edmund Clarke, Christopher Bentham, Nikola Prtljaga, Igor E. Itskevich, Luke R. Wilson, Maurice S. Skolnick, A. Mark Fox

    On-chip single-photon sources are key components for integrated photonic quantum technologies. Semiconductor quantum dots can exhibit near-ideal single-photon emission, but this can be significantly degraded in on-chip geometries owing to nearby etched surfaces. A long-proposed solution to improve the indistinguishablility is to use the Purcell effect to reduce the radiative lifetime. However, until now only modest Purcell enhancements have been observed. Here we use pulsed resonant excitation to eliminate slow relaxation paths, revealing a highly Purcell-shortened radiative lifetime (22.7 ps) in a waveguide-coupled quantum dot–photonic crystal cavity system. This leads to near-lifetime-limited single-photon emission that retains high indistinguishablility (93.9%) on a timescale in which 20 photons may be emitted. Nearly background-free pulsed resonance fluorescence is achieved under π-pulse excitation, enabling demonstration of an on-chip, on-demand single-photon source with very high potential repetition rates.

    更新日期:2018-07-18
  • The need for levering heat
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16
    Christian Van den Broeck

    The need for levering heat The need for levering heat, Published online: 16 July 2018; doi:10.1038/s41565-018-0210-3 A quantum dot device reaches close to optimal thermoelectric efficiency by working with electrons that lever heat.

    更新日期:2018-07-18
  • Publisher Correction: Factors that make an impact
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-16

    Publisher Correction: Factors that make an impactPublisher Correction: Factors that make an impact, Published online: 16 July 2018; doi:10.1038/s41565-018-0225-9Publisher Correction: Factors that make an impact

    更新日期:2018-07-16
  • Graphene quantum dots prevent α-synucleinopathy in Parkinson’s disease
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-09
    Donghoon Kim, Je Min Yoo, Heehong Hwang, Junghee Lee, Su Hyun Lee, Seung Pil Yun, Myung Jin Park, MinJun Lee, Seulah Choi, Sang Ho Kwon, Saebom Lee, Seung-Hwan Kwon, Sangjune Kim, Yong Joo Park, Misaki Kinoshita, Young-Ho Lee, Seokmin Shin, Seung R. Paik, Sung Joong Lee, Seulki Lee, Byung Hee Hong, Han Seok Ko

    Graphene quantum dots prevent α-synucleinopathy in Parkinson’s disease Graphene quantum dots prevent α-synucleinopathy in Parkinson’s disease, Published online: 09 July 2018; doi:10.1038/s41565-018-0179-y Graphene quantum dots inhibit the formation of alpha-synuclein fibrils and induce their dissociation in vitro, and display neuro-protective properties in in vivo models of Parkinson’s disease, with no appreciable long-term toxicity.

    更新日期:2018-07-10
  • Advanced tools for the safety assessment of nanomaterials
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Bengt Fadeel, Lucian Farcal, Barry Hardy, Socorro Vázquez-Campos, Danail Hristozov, Antonio Marcomini, Iseult Lynch, Eugenia Valsami-Jones, Harri Alenius, Kai Savolainen

    Engineered nanomaterials (ENMs) have tremendous potential to produce beneficial technological impact in numerous sectors in society. Safety assessment is, of course, of paramount importance. However, the myriad variations of ENM properties makes the identification of specific features driving toxicity challenging. At the same time, reducing animal tests by introducing alternative and/or predictive in vitro and in silico methods has become a priority. It is important to embrace these new advances in the safety assessment of ENMs. Indeed, remarkable progress has been made in recent years with respect to mechanism-based hazard assessment of ENMs, including systems biology approaches as well as high-throughput screening platforms, and new tools are also emerging in risk assessment and risk management for humans and the environment across the whole life-cycle of nano-enabled products. Here, we highlight some of the key advances in the hazard and risk assessment of ENMs.

    更新日期:2018-07-08
  • Low-dimensional perovskites
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Olga Bubnova

    Low-dimensional perovskitesLow-dimensional perovskites, Published online: 06 July 2018; doi:10.1038/s41565-018-0214-zLow-dimensional perovskites

    更新日期:2018-07-08
  • Setting up boundaries
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Chiara Pastore

    Setting up boundariesSetting up boundaries, Published online: 06 July 2018; doi:10.1038/s41565-018-0212-1Setting up boundaries

    更新日期:2018-07-08
  • Factors that make an impact
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06

    Factors that make an impactFactors that make an impact, Published online: 06 July 2018; doi:10.1038/s41565-018-0215-yNumber of citations in academic papers is not always a good measure for the influence of applied research papers.

    更新日期:2018-07-08
  • Plastic not so fantastic
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Fabio Pulizzi

    Plastic not so fantasticPlastic not so fantastic, Published online: 06 July 2018; doi:10.1038/s41565-018-0213-0Plastic not so fantastic

    更新日期:2018-07-08
  • Listening
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Chris Toumey

    ListeningListening, Published online: 06 July 2018; doi:10.1038/s41565-018-0199-7Chris Toumey explores the potential of sound as a way to investigate nature at the nanoscale.

    更新日期:2018-07-08
  • From an idea to a technology
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Alberto Moscatelli

    From an idea to a technologyFrom an idea to a technology, Published online: 06 July 2018; doi:10.1038/s41565-018-0206-zNature Nanotechnology has asked Jong-Hyun Ahn, Yi Cui and Hagan Bayley, corresponding authors of the three papers published in the journal that have received the highest number of citations in the patent literature, to share their insights about doing applied research in academia and whatit takes to transform an idea into a viable technology.

    更新日期:2018-07-08
  • Strong bundles based on carbon nanotubes
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-06
    Rodney S. Ruoff

    Strong bundles based on carbon nanotubesStrong bundles based on carbon nanotubes, Published online: 06 July 2018; doi:10.1038/s41565-018-0184-1Long bundles of defect-free carbon nanotubes can exhibit exceptionally high strength.

    更新日期:2018-07-08
  • Metallic supercurrent field-effect transistor
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-02
    Giorgio De Simoni, Federico Paolucci, Paolo Solinas, Elia Strambini, Francesco Giazotto

    In their original formulation of superconductivity, the London brothers predicted1 the exponential suppression of an electrostatic field inside a superconductor over the so-called London penetration depth2,3,4, λL. Despite a few experiments indicating hints of perturbation induced by electrostatic fields5,6,7, no clue has been provided so far on the possibility to manipulate metallic superconductors via the field effect. Here, we report field-effect control of the supercurrent in all-metallic transistors made of different Bardeen–Cooper–Schrieffer superconducting thin films. At low temperature, our field-effect transistors show a monotonic decay of the critical current under increasing electrostatic field up to total quenching for gate voltage values as large as ±40 V in titanium-based devices. This bipolar field effect persists up to ~85% of the critical temperature (~0.41 K), and in the presence of sizable magnetic fields. A similar behaviour is observed in aluminium thin-film field-effect transistors. A phenomenological theory accounts for our observations, and points towards the interpretation in terms of an electric-field-induced perturbation propagating inside the superconducting film. In our understanding, this affects the pairing potential and quenches the supercurrent. These results could represent a groundbreaking asset for the realization of all-metallic superconducting field-effect electronics and leading-edge quantum information architectures8,9.

    更新日期:2018-07-02
  • Low-voltage electrostatic modulation of ion diffusion through layered graphene-based nanoporous membranes
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-02
    Chi Cheng, Gengping Jiang, George Philip Simon, Jefferson Zhe Liu, Dan Li

    Ion transport in nanoconfinement differs from that in bulk and has been extensively researched across scientific and engineering disciplines1,2,3,4. For many energy and water applications of nanoporous materials, concentration-driven ion diffusion is simultaneously subjected to a local electric field arising from surface charge or an externally applied potential. Due to the uniquely crowded intermolecular forces under severe nanoconfinement (<2 nm), the transport behaviours of ions can be influenced by the interfacial electrical double layer (EDL) induced by a surface potential, with complex implications, engendering unusual ion dynamics5,6,7. However, it remains an experimental challenge to investigate how such a surface potential and its coupling with nanoconfinement manipulate ion diffusion. Here, we exploit the tunable nanoconfinement in layered graphene-based nanoporous membranes to show that sub-2 nm confined ion diffusion can be strongly modulated by the surface potential-induced EDL. Depending on the potential sign, the combination and concentration of ion pairs, diffusion rates can be reversibly modulated and anomalously enhanced by 4~7 times within 0.5 volts, across a salt concentration gradient up to seawater salinity. Modelling suggests that this anomalously enhanced diffusion is related to the strong ion–ion correlations under severe nanoconfinement, and cannot be explained by conventional theoretical predictions.

    更新日期:2018-07-02
  • Electric-field control of magnetism in a few-layered van der Waals ferromagnetic semiconductor
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-07-02
    Zhi Wang, Tongyao Zhang, Mei Ding, Baojuan Dong, Yanxu Li, Maolin Chen, Xiaoxi Li, Jianqi Huang, Hanwen Wang, Xiaotian Zhao, Yong Li, Da Li, Chuankun Jia, Lidong Sun, Huaihong Guo, Yu Ye, Dongming Sun, Yuansen Chen, Teng Yang, Jing Zhang, Shimpei Ono, Zheng Han, Zhidong Zhang

    Manipulating a quantum state via electrostatic gating has been of great importance for many model systems in nanoelectronics. Until now, however, controlling the electron spins or, more specifically, the magnetism of a system by electric-field tuning has proven challenging1,2,3,4. Recently, atomically thin magnetic semiconductors have attracted significant attention due to their emerging new physical phenomena5,6,7,8,9,10,11,12,13. However, many issues are yet to be resolved to convincingly demonstrate gate-controllable magnetism in these two-dimensional materials. Here, we show that, via electrostatic gating, a strong field effect can be observed in devices based on few-layered ferromagnetic semiconducting Cr2Ge2Te6. At different gate doping, micro-area Kerr measurements in the studied devices demonstrate bipolar tunable magnetization loops below the Curie temperature, which is tentatively attributed to the moment rebalance in the spin-polarized band structure. Our findings of electric-field-controlled magnetism in van der Waals magnets show possibilities for potential applications in new-generation magnetic memory storage, sensors and spintronics.

    更新日期:2018-07-02
  • Tailoring sample-wide pseudo-magnetic fields on a graphene–black phosphorus heterostructure
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-25
    Yanpeng Liu, J. N. B. Rodrigues, Yong Zheng Luo, Linjun Li, Alexandra Carvalho, Ming Yang, Evan Laksono, Junpeng Lu, Yang Bao, Hai Xu, Sherman J. R. Tan, Zhizhan Qiu, Chorng Haur Sow, Yuan Ping Feng, A. H. Castro Neto, Shaffique Adam, Jiong Lu, Kian Ping Loh

    Spatially tailored pseudo-magnetic fields (PMFs) can give rise to pseudo-Landau levels and the valley Hall effect in graphene. At an experimental level, it is highly challenging to create the specific strain texture that can generate PMFs over large areas. Here, we report that superposing graphene on multilayer black phosphorus creates shear-strained superlattices that generate a PMF over an entire graphene–black phosphorus heterostructure with edge size of tens of micrometres. The PMF is intertwined with the spatial period of the moiré pattern, and its spatial distribution and intensity can be modified by changing the relative orientation of the two materials. We show that the emerging pseudo-Landau levels influence the transport properties of graphene–black phosphorus field-effect transistor devices with Hall bar geometry. The application of an external magnetic field allows us to enhance or reduce the effective field depending on the valley polarization with the prospect of developing a valley filter.

    更新日期:2018-06-27
  • A heterogeneous single-atom palladium catalyst surpassing homogeneous systems for Suzuki coupling
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-25
    Zupeng Chen, Evgeniya Vorobyeva, Sharon Mitchell, Edvin Fako, Manuel A. Ortuño, Núria López, Sean M. Collins, Paul A. Midgley, Sylvia Richard, Gianvito Vilé, Javier Pérez-Ramírez

    Palladium-catalysed cross-coupling reactions, central tools in fine-chemical synthesis, predominantly employ soluble metal complexes despite recognized challenges with product purification and catalyst reusability1,2,3. Attempts to tether these homogeneous catalysts on insoluble carriers have been thwarted by suboptimal stability, which leads to a progressively worsening performance due to metal leaching or clustering4. The alternative application of supported Pd nanoparticles has faced limitations because of insufficient activity under the mild conditions required to avoid thermal degradation of the substrates or products. Single-atom heterogeneous catalysts lie at the frontier5,6,7,8,9,10,11,12,13,14,15,16,17,18. Here, we show that the Pd atoms anchored on exfoliated graphitic carbon nitride (Pd-ECN) capture the advantages of both worlds, as they comprise a solid catalyst that matches the high chemoselectivity and broad functional group tolerance of state-of-the-art homogeneous catalysts for Suzuki couplings, and also demonstrate a robust stability in flow. The adaptive coordination environment within the macroheterocycles of ECN facilitates each catalytic step. The findings illustrate the exciting opportunities presented by nanostructuring single atoms in solid hosts for catalytic processes that remain difficult to heterogenize.

    更新日期:2018-06-27
  • Pathway-controlled formation of mesostructured all-DNA colloids and superstructures
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-25
    Rémi Merindol, Sebastian Loescher, Avik Samanta, Andreas Walther

    DNA has traditionally been used for the programmable design of nanostructures by exploiting its sequence-defined supramolecular recognition. However, control on larger length scales or even hierarchical materials that translate to the macroscale remain difficult to construct. Here, we show that the polymer character of single-stranded DNA (ssDNA) can be activated via a nucleobase-specific lower critical solution temperature, which provides a unique access to mesoscale structuring mechanisms on larger length scales. We integrate both effects into ssDNA multiblock copolymers that code sequences for phase separation, hybridization and functionalization. Kinetic pathway guidance using temperature ramps balances the counteracting mesoscale phase separation during heating with nanoscale duplex recognition during cooling to yield a diversity of complex all-DNA colloids with control over the internal dynamics and of their superstructures. Our approach provides a facile and versatile platform to add mesostructural layers into hierarchical all-DNA materials. The high density of addressable ssDNA blocks opens routes for applications such as gene delivery, artificial evolution or spatially encoded (bio)materials.

    更新日期:2018-06-27
  • Getting to the brain
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-19
    Maria Giuseppina Baratta

    Getting to the brain Getting to the brain, Published online: 19 June 2018; doi:10.1038/s41565-018-0182-3 Getting to the brain

    更新日期:2018-06-19
  • Publisher Correction: Nanobiophotonics: Nature-inspired sensors
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-19
    Wolfgang Fink

    Publisher Correction: Nanobiophotonics: Nature-inspired sensors Publisher Correction: Nanobiophotonics: Nature-inspired sensors, Published online: 19 June 2018; doi:10.1038/s41565-018-0201-4 Publisher Correction: Nanobiophotonics: Nature-inspired sensors

    更新日期:2018-06-19
  • Antibody orientation determines corona mistargeting capability
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Morteza Mahmoudi

    Antibody orientation determines corona mistargeting capability Antibody orientation determines corona mistargeting capability, Published online: 18 June 2018; doi:10.1038/s41565-018-0147-6 Antibody pre-adsorption can reduce the adverse effects of the biomolecular corona.

    更新日期:2018-06-18
  • Continuous-wave upconverting nanoparticle microlasers
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Angel Fernandez-Bravo, Kaiyuan Yao, Edward S. Barnard, Nicholas J. Borys, Elizabeth S. Levy, Bining Tian, Cheryl A. Tajon, Luca Moretti, M. Virginia Altoe, Shaul Aloni, Kenes Beketayev, Francesco Scotognella, Bruce E. Cohen, Emory M. Chan, P. James Schuck

    Reducing the size of lasers to microscale dimensions enables new technologies1 that are specifically tailored for operation in confined spaces ranging from ultra-high-speed microprocessors2 to live brain tissue3. However, reduced cavity sizes increase optical losses and require greater input powers to reach lasing thresholds. Multiphoton-pumped lasers4,5,6,7 that have been miniaturized using nanomaterials such as lanthanide-doped upconverting nanoparticles (UCNPs)8 as lasing media require high pump intensities to achieve ultraviolet and visible emission and therefore operate under pulsed excitation schemes. Here, we make use of the recently described energy-looping excitation mechanism in Tm3+-doped UCNPs9 to achieve continuous-wave upconverted lasing action in stand-alone microcavities at excitation fluences as low as 14 kW cm−2. Continuous-wave lasing is uninterrupted, maximizing signal and enabling modulation of optical interactions10. By coupling energy-looping nanoparticles to whispering-gallery modes of polystyrene microspheres, we induce stable lasing for more than 5 h at blue and near-infrared wavelengths simultaneously. These microcavities are excited in the biologically transmissive second near-infrared (NIR-II) window and are small enough to be embedded in organisms, tissues or devices. The ability to produce continuous-wave lasing in microcavities immersed in blood serum highlights practical applications of these microscale lasers for sensing and illumination in complex biological environments.

    更新日期:2018-06-18
  • Energy harvesting from lukewarm photons
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Philippe Ben-Abdallah

    Energy harvesting from lukewarm photons Energy harvesting from lukewarm photons, Published online: 18 June 2018; doi:10.1038/s41565-018-0180-5 Evanescent photons of a hot body at a temperature below 500 K can be efficiently converted into electricity in a near-field thermophotovoltaic device.

    更新日期:2018-06-18
  • Pre-adsorption of antibodies enables targeting of nanocarriers despite a biomolecular corona
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Manuel Tonigold, Johanna Simon, Diego Estupiñán, Maria Kokkinopoulou, Jonas Reinholz, Ulrike Kintzel, Anke Kaltbeitzel, Patricia Renz, Matthias P. Domogalla, Kerstin Steinbrink, Ingo Lieberwirth, Daniel Crespy, Katharina Landfester, Volker Mailänder

    To promote drug delivery to exact sites and cell types, the surface of nanocarriers is functionalized with targeting antibodies or ligands, typically coupled by covalent chemistry. Once the nanocarrier is exposed to biological fluid such as plasma, however, its surface is inevitably covered with various biomolecules forming the protein corona, which masks the targeting ability of the nanoparticle. Here, we show that we can use a pre-adsorption process to attach targeting antibodies to the surface of the nanocarrier. Pre-adsorbed antibodies remain functional and are not completely exchanged or covered by the biomolecular corona, whereas coupled antibodies are more affected by this shielding. We conclude that pre-adsorption is potentially a versatile, efficient and rapid method of attaching targeting moieties to the surface of nanocarriers.

    更新日期:2018-06-18
  • Nanogap near-field thermophotovoltaics
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Anthony Fiorino, Linxiao Zhu, Dakotah Thompson, Rohith Mittapally, Pramod Reddy, Edgar Meyhofer

    Conversion of heat to electricity via solid-state devices is of great interest and has led to intense research of thermoelectric materials1,2. Alternative approaches for solid-state heat-to-electricity conversion include thermophotovoltaic (TPV) systems where photons from a hot emitter traverse a vacuum gap and are absorbed by a photovoltaic (PV) cell to generate electrical power. In principle, such systems may also achieve higher efficiencies and offer more versatility in use. However, the typical temperature of the hot emitter remains too low (<1,000 K) to achieve a sufficient photon flux to the PV cell, limiting practical applications. Theoretical proposals3,4,5,6,7,8,9,10,11,12 suggest that near-field (NF) effects13,14,15,16,17,18 that arise in nanoscale gaps may be leveraged to increase the photon flux to the PV cell and significantly enhance the power output. Here, we describe functional NFTPV devices consisting of a microfabricated system and a custom-built nanopositioner and demonstrate an ~40-fold enhancement in the power output at nominally 60 nm gaps relative to the far field. We systematically characterize this enhancement over a range of gap sizes and emitter temperatures, and for PV cells with two different bandgap energies. We anticipate that this technology, once optimized, will be viable for waste heat recovery applications.

    更新日期:2018-06-18
  • Taking upconversion to lase in microcavity
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-18
    Gungun Lin, Dayong Jin

    Taking upconversion to lase in microcavity Taking upconversion to lase in microcavity, Published online: 18 June 2018; doi:10.1038/s41565-018-0191-2 Stable, sharp-bandwidth and upconverted stimulated emissions are generated from a 5-μm polystyrene cavity pumped by a low-power continuous-wave excitation.

    更新日期:2018-06-18
  • Fast thermal relaxation in cavity-coupled graphene bolometers with a Johnson noise read-out
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-11
    Dmitri K. Efetov, Ren-Jye Shiue, Yuanda Gao, Brian Skinner, Evan D. Walsh, Hyeongrak Choi, Jiabao Zheng, Cheng Tan, Gabriele Grosso, Cheng Peng, James Hone, Kin Chung Fong, Dirk Englund

    High sensitivity, fast response time and strong light absorption are the most important metrics for infrared sensing and imaging. The trade-off between these characteristics remains the primary challenge in bolometry. Graphene with its unique combination of a record small electronic heat capacity and a weak electron–phonon coupling has emerged as a sensitive bolometric medium that allows for high intrinsic bandwidths1–3. Moreover, the material’s light absorption can be enhanced to near unity by integration into photonic structures. Here, we introduce an integrated hot-electron bolometer based on Johnson noise readout of electrons in ultra-clean hexagonal-boron-nitride-encapsulated graphene, which is critically coupled to incident radiation through a photonic nanocavity with Q = 900. The device operates at telecom wavelengths and shows an enhanced bolometric response at charge neutrality. At 5 K, we obtain a noise equivalent power of about 10 pW Hz–1/2, a record fast thermal relaxation time, <35 ps, and an improved light absorption. However the device can operate even above 300 K with reduced sensitivity. We work out the performance mechanisms and limits of the graphene bolometer and give important insights towards the potential development of practical applications.

    更新日期:2018-06-12
  • Switchable geometric frustration in an artificial-spin-ice–superconductor heterosystem
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-11
    Yong-Lei Wang, Xiaoyu Ma, Jing Xu, Zhi-Li Xiao, Alexey Snezhko, Ralu Divan, Leonidas E. Ocola, John E. Pearson, Boldizsar Janko, Wai-Kwong Kwok

    Geometric frustration emerges when local interaction energies in an ordered lattice structure cannot be simultaneously minimized, resulting in a large number of degenerate states. The numerous degenerate configurations may lead to practical applications in microelectronics1, such as data storage, memory and logic2. However, it is difficult to achieve very high degeneracy, especially in a two-dimensional system3,4. Here, we showcase in situ controllable geometric frustration with high degeneracy in a two-dimensional flux-quantum system. We create this in a superconducting thin film placed underneath a reconfigurable artificial-spin-ice structure5. The tunable magnetic charges in the artificial-spin-ice strongly interact with the flux quanta in the superconductor, enabling switching between frustrated and crystallized flux quanta states. The different states have measurable effects on the superconducting critical current profile, which can be reconfigured by precise selection of the spin-ice magnetic state through the application of an external magnetic field. We demonstrate the applicability of these effects by realizing a reprogrammable flux quanta diode. The tailoring of the energy landscape of interacting ‘particles’ using artificial-spin-ices provides a new paradigm for the design of geometric frustration, which could illuminate a path to control new functionalities in other material systems, such as magnetic skyrmions6, electrons and holes in two-dimensional materials7,8, and topological insulators9, as well as colloids in soft materials10,11,12,13.

    更新日期:2018-06-12
  • Single-layer graphene modulates neuronal communication and augments membrane ion currents
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-11
    Niccolò Paolo Pampaloni, Martin Lottner, Michele Giugliano, Alessia Matruglio, Francesco D’Amico, Maurizio Prato, Josè Antonio Garrido, Laura Ballerini, Denis Scaini

    The use of graphene-based materials to engineer sophisticated biosensing interfaces that can adapt to the central nervous system requires a detailed understanding of how such materials behave in a biological context. Graphene’s peculiar properties can cause various cellular changes, but the underlying mechanisms remain unclear. Here, we show that single-layer graphene increases neuronal firing by altering membrane-associated functions in cultured cells. Graphene tunes the distribution of extracellular ions at the interface with neurons, a key regulator of neuronal excitability. The resulting biophysical changes in the membrane include stronger potassium ion currents, with a shift in the fraction of neuronal firing phenotypes from adapting to tonically firing. By using experimental and theoretical approaches, we hypothesize that the graphene–ion interactions that are maximized when single-layer graphene is deposited on electrically insulating substrates are crucial to these effects.

    更新日期:2018-06-12
  • From scientist to editor
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Kostya S. Novoselov, Fabio Pulizzi

    From scientist to editor From scientist to editor, Published online: 06 June 2018; doi:10.1038/s41565-018-0170-7 Kostya S. Novoselov, professor of physics at the University of Manchester, UK, has been digging into the details of the life of an editor by asking Fabio Pulizzi, Chief Editor of Nature Nanotechnology, some inside information on his work.

    更新日期:2018-06-07
  • Confining light to the atomic scale
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Alberto G. Curto, Jaime Gómez Rivas

    Confining light to the atomic scale Confining light to the atomic scale, Published online: 06 June 2018; doi:10.1038/s41565-018-0166-3 A graphene sheet near a metal nanoantenna squeezes infrared photons into a subnanometric gap, pushing the limits of nanophotonics.

    更新日期:2018-06-07
  • Selectivity in one click
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Alberto Moscatelli

    Selectivity in one click Selectivity in one click, Published online: 06 June 2018; doi:10.1038/s41565-018-0173-4 Selectivity in one click

    更新日期:2018-06-07
  • Borophene as a prototype for synthetic 2D materials development
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Andrew J. Mannix, Zhuhua Zhang, Nathan P. Guisinger, Boris I. Yakobson, Mark C. Hersam

    The synthesis of 2D materials with no analogous bulk layered allotropes promises a substantial breadth of physical and chemical properties through the diverse structural options afforded by substrate-dependent epitaxy. However, despite the joint theoretical and experimental efforts to guide materials discovery, successful demonstrations of synthetic 2D materials have been rare. The recent synthesis of 2D boron polymorphs (that is, borophene) provides a notable example of such success. In this Perspective, we discuss recent progress and future opportunities for borophene research. Borophene combines unique mechanical properties with anisotropic metallicity, which complements the canon of conventional 2D materials. The multi-centre characteristics of boron–boron bonding lead to the formation of configurationally varied, vacancy-mediated structural motifs, providing unprecedented diversity in a mono-elemental 2D system with potential for electronic applications, chemical functionalization, materials synthesis and complex heterostructures. With its foundations in computationally guided synthesis, borophene can serve as a prototype for ongoing efforts to discover and exploit synthetic 2D materials.

    更新日期:2018-06-07
  • Diagnose lithium battery
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Wenjie Sun

    Diagnose lithium battery Diagnose lithium battery, Published online: 06 June 2018; doi:10.1038/s41565-018-0176-1 Diagnose lithium battery

    更新日期:2018-06-07
  • Nature-inspired sensors
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Wolfgang Fink

    Nature-inspired sensors Nature-inspired sensors, Published online: 06 June 2018; doi:10.1038/s41565-018-0164-5 Biomimetic devices that mimic butterfly wing nanostructures will help the fight against glaucoma.

    更新日期:2018-06-07
  • Spinning the spin
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06
    Benjamin Heinrich

    Spinning the spin Spinning the spin, Published online: 06 June 2018; doi:10.1038/s41565-018-0174-3 Spinning the spin

    更新日期:2018-06-07
  • Bacterial nanotechnology
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-06

    Bacterial nanotechnology Bacterial nanotechnology, Published online: 06 June 2018; doi:10.1038/s41565-018-0177-0 The 2018 Kavli Prize recognizes scientists working in the field of basic biology and reminds us of the importance of fundamental research for uncovering the technologies of the future.

    更新日期:2018-06-07
  • A scalable multi-photon coincidence detector based on superconducting nanowires
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-06-04
    Di Zhu, Qing-Yuan Zhao, Hyeongrak Choi, Tsung-Ju Lu, Andrew E. Dane, Dirk Englund, Karl K. Berggren

    Coincidence detection of single photons is crucial in numerous quantum technologies and usually requires multiple time-resolved single-photon detectors. However, the electronic readout becomes a major challenge when the measurement basis scales to large numbers of spatial modes. Here, we address this problem by introducing a two-terminal coincidence detector that enables scalable readout of an array of detector segments based on superconducting nanowire microstrip transmission line. Exploiting timing logic, we demonstrate a sixteen-element detector that resolves all 136 possible single-photon and two-photon coincidence events. We further explore the pulse shapes of the detector output and resolve up to four-photon events in a four-element device, giving the detector photon-number-resolving capability. This new detector architecture and operating scheme will be particularly useful for multi-photon coincidence detection in large-scale photonic integrated circuits.

    更新日期:2018-06-05
  • Publisher Correction: Direct imaging of the electron liquid at oxide interfaces
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-30
    Kyung Song, Sangwoo Ryu, Hyungwoo Lee, Tula R. Paudel, Christoph T. Koch, Bumsu Park, Ja Kyung Lee, Si-Young Choi, Young-Min Kim, Jong Chan Kim, Hu Young Jeong, Mark S. Rzchowski, Evgeny Y. Tsymbal, Chang-Beom Eom, Sang Ho Oh

    Publisher Correction: Direct imaging of the electron liquid at oxide interfaces Publisher Correction: Direct imaging of the electron liquid at oxide interfaces, Published online: 30 May 2018; doi:10.1038/s41565-018-0137-8 Publisher Correction: Direct imaging of the electron liquid at oxide interfaces

    更新日期:2018-05-31
  • DNA scaffolds support stable and uniform peptide nanopores
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-28
    Evan Spruijt, Samuel E. Tusk, Hagan Bayley

    The assembly of peptides into membrane-spanning nanopores might be promoted by scaffolds to pre-organize the structures. Such scaffolds could enable the construction of uniform pores of various sizes and pores with controlled permutations around a central axis. Here, we show that DNA nanostructures can serve as scaffolds to arrange peptides derived from the octameric polysaccharide transporter Wza to form uniform nanopores in planar lipid bilayers. Our ring-shaped DNA scaffold is assembled from short synthetic oligonucleotides that are connected to Wza peptides through flexible linkers. When scaffolded, the Wza peptides form conducting nanopores of which only octamers are stable and of uniform conductance. Removal of the DNA scaffold by cleavage of the linkers leads to a rapid loss of the nanopores from the lipid bilayer, which shows that the scaffold is essential for their stability. The DNA scaffold also adds functionality to the nanopores by enabling reversible and permanent binding of complementary tagged oligonucleotides near the nanopore entrance.

    更新日期:2018-05-29
  • Electric switching of magnetism in 2D
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-23
    Kenneth S. Burch

    Electric switching of magnetism in 2D Electric switching of magnetism in 2D, Published online: 23 May 2018; doi:10.1038/s41565-018-0165-4 Combined electrostatic gating and magnetic fields switch a 2D atomic crystal from an antiferromagnetic to a ferromagnetic state.

    更新日期:2018-05-23
  • Publisher Correction: Quantum engineering of transistors based on 2D materials heterostructures
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-22
    Giuseppe Iannaccone, Francesco Bonaccorso, Luigi Colombo, Gianluca Fiori

    Publisher Correction: Quantum engineering of transistors based on 2D materials heterostructures Publisher Correction: Quantum engineering of transistors based on 2D materials heterostructures, Published online: 22 May 2018; doi:10.1038/s41565-018-0136-9 Publisher Correction: Quantum engineering of transistors based on 2D materials heterostructures

    更新日期:2018-05-23
  • Single entity resolution valving of nanoscopic species in liquids
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-21
    Patric Eberle, Christian Höller, Philipp Müller, Maarit Suomalainen, Urs F. Greber, Hadi Eghlidi, Dimos Poulikakos

    Investigating biological and synthetic nanoscopic species in liquids, at the ultimate resolution of single entity, is important in diverse fields1,2,3,4,5. Progress has been made6,7,8,9,10, but significant barriers need to be overcome such as the need for intense fields, the lack of versatility in operating conditions and the limited functionality in solutions of high ionic strength for biological applications. Here, we demonstrate switchable electrokinetic nanovalving able to confine and guide single nano-objects, including macromolecules, with sizes down to around 10 nanometres, in a lab-on-chip environment. The nanovalves are based on spatiotemporal tailoring of the potential energy landscape of nano-objects using an electric field, modulated collaboratively by wall nanotopography and by embedded electrodes in a nanochannel system. We combine nanovalves to isolate single entities from an ensemble, and demonstrate their guiding, confining, releasing and sorting. We show on-demand motion control of single immunoglobulin G molecules, quantum dots, adenoviruses, lipid vesicles, dielectric and metallic particles, suspended in electrolytes with a broad range of ionic strengths, up to biological levels. Such systems can enable nanofluidic, large-scale integration and individual handling of multiple entities in applications ranging from single species characterization and screening to in situ chemical or biochemical synthesis in continuous on-chip processes.

    更新日期:2018-05-22
  • Broadband, electrically tunable third-harmonic generation in graphene
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-21
    Giancarlo Soavi, Gang Wang, Habib Rostami, David G. Purdie, Domenico De Fazio, Teng Ma, Birong Luo, Junjia Wang, Anna K. Ott, Duhee Yoon, Sean A. Bourelle, Jakob E. Muench, Ilya Goykhman, Stefano Dal Conte, Michele Celebrano, Andrea Tomadin, Marco Polini, Giulio Cerullo, Andrea C. Ferrari

    Optical harmonic generation occurs when high intensity light (>1010 W m–2) interacts with a nonlinear material. Electrical control of the nonlinear optical response enables applications such as gate-tunable switches and frequency converters. Graphene displays exceptionally strong light–matter interaction and electrically and broadband tunable third-order nonlinear susceptibility. Here, we show that the third-harmonic generation efficiency in graphene can be increased by almost two orders of magnitude by controlling the Fermi energy and the incident photon energy. This enhancement is due to logarithmic resonances in the imaginary part of the nonlinear conductivity arising from resonant multiphoton transitions. Thanks to the linear dispersion of the massless Dirac fermions, gate controllable third-harmonic enhancement can be achieved over an ultrabroad bandwidth, paving the way for electrically tunable broadband frequency converters for applications in optical communications and signal processing.

    更新日期:2018-05-22
  • Author Correction: Ultrahard carbon film from epitaxial two-layer graphene
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-21
    Yang Gao, Tengfei Cao, Filippo Cellini, Claire Berger, Walter A. de Heer, Erio Tosatti, Elisa Riedo, Angelo Bongiorno

    Author Correction: Ultrahard carbon film from epitaxial two-layer graphene Author Correction: Ultrahard carbon film from epitaxial two-layer graphene, Published online: 21 May 2018; doi:10.1038/s41565-018-0158-3 Author Correction: Ultrahard carbon film from epitaxial two-layer graphene

    更新日期:2018-05-22
  • High-speed photothermal off-resonance atomic force microscopy reveals assembly routes of centriolar scaffold protein SAS-6
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-21
    Adrian P. Nievergelt, Niccolò Banterle, Santiago H. Andany, Pierre Gönczy, Georg E. Fantner

    The self-assembly of protein complexes is at the core of many fundamental biological processes1, ranging from the polymerization of cytoskeletal elements, such as microtubules2, to viral capsid formation and organelle assembly3. To reach a comprehensive understanding of the underlying mechanisms of self-assembly, high spatial and temporal resolutions must be attained. This is complicated by the need to not interfere with the reaction during the measurement. As self-assemblies are often governed by weak interactions, they are especially difficult to monitor with high-speed atomic force microscopy (HS-AFM) due to the non-negligible tip–sample interaction forces involved in current methods. We have developed a HS-AFM technique, photothermal off-resonance tapping (PORT), which is gentle enough to monitor self-assembly reactions driven by weak interactions. We apply PORT to dissect the self-assembly reaction of SAS-6 proteins, which form a nine-fold radially symmetric ring-containing structure that seeds the formation of the centriole organelle. Our analysis reveals the kinetics of SAS-6 ring formation and demonstrates that distinct biogenesis routes can be followed to assemble a nine-fold symmetrical structure.

    更新日期:2018-05-22
  • Publisher Correction: Tunnelling spectroscopy of gate-induced superconductivity in MoS2
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-17
    Davide Costanzo, Haijing Zhang, Bojja Aditya Reddy, Helmuth Berger, Alberto F. Morpurgo

    Publisher Correction: Tunnelling spectroscopy of gate-induced superconductivity in MoS2 Publisher Correction: Tunnelling spectroscopy of gate-induced superconductivity in MoS2, Published online: 17 May 2018; doi:10.1038/s41565-018-0159-2 Publisher Correction: Tunnelling spectroscopy of gate-induced superconductivity in MoS2

    更新日期:2018-05-18
  • Carbon nanotube bundles with tensile strength over 80 GPa
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-14
    Yunxiang Bai, Rufan Zhang, Xuan Ye, Zhenxing Zhu, Huanhuan Xie, Boyuan Shen, Dali Cai, Bofei Liu, Chenxi Zhang, Zhao Jia, Shenli Zhang, Xide Li, Fei Wei

    Carbon nanotubes (CNTs) are one of the strongest known materials. When assembled into fibres, however, their strength becomes impaired by defects, impurities, random orientations and discontinuous lengths. Fabricating CNT fibres with strength reaching that of a single CNT has been an enduring challenge. Here, we demonstrate the fabrication of CNT bundles (CNTBs) that are centimetres long with tensile strength over 80 GPa using ultralong defect-free CNTs. The tensile strength of CNTBs is controlled by the Daniels effect owing to the non-uniformity of the initial strains in the components. We propose a synchronous tightening and relaxing strategy to release these non-uniform initial strains. The fabricated CNTBs, consisting of a large number of components with parallel alignment, defect-free structures, continuous lengths and uniform initial strains, exhibit a tensile strength of 80 GPa (corresponding to an engineering tensile strength of 43 GPa), which is far higher than that of any other strong fibre.

    更新日期:2018-05-15
  • Combination of fucoidan-based magnetic nanoparticles and immunomodulators enhances tumour-localized immunotherapy
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-14
    Chih-Sheng Chiang, Yu-Jung Lin, Rachel Lee, Yen-Ho Lai, Hung-Wei Cheng, Chia-Hung Hsieh, Woei-Cherng Shyu, San-Yuan Chen

    Checkpoint immunotherapy that inhibits tumour immune evasion has demonstrated significant clinical success. However, the therapeutic response is limited to certain patient populations, and immunotoxicity as well as autoimmunity have compromised the therapeutic benefits. Here, we report on an inherently therapeutic fucoidan–dextran-based magnetic nanomedicine (IO@FuDex3) conjugated with a checkpoint inhibitor (anti-PD-L1) and T-cell activators (anti-CD3 and anti-CD28). IO@FuDex3 can repair the immunosuppressive tumour microenvironment by reinvigorating tumour-infiltrating lymphocytes, while targeting the nanomedicine via magnetic navigation to the tumour to minimize off-target effects. Treatment that combines IO@FuDex3 and magnetic navigation reduces the occurrence of adverse events and extends the median survival from 32 to 63 days with less than 1 per cent dose compared with soluble anti-PD-L1. Thus, we demonstrate the potential of integrating anti-PD-L1 and T-cell activators as a form of inherently therapeutic nanomedicine to augment the therapeutic index of combination checkpoint immunotherapy.

    更新日期:2018-05-15
  • Robotic assembly of artificial nanomaterials
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-14
    Riccardo Frisenda, Andres Castellanos-Gomez

    Robotic assembly of artificial nanomaterials Robotic assembly of artificial nanomaterials, Published online: 14 May 2018; doi:10.1038/s41565-018-0156-5 An automated robotic system is capable of assembling 2D van der Waals heterostructures of unprecedented complexity in a timely fashion.

    更新日期:2018-05-15
  • Exfoliation of a non-van der Waals material from iron ore hematite
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-07
    Aravind Puthirath Balan, Sruthi Radhakrishnan, Cristiano F. Woellner, Shyam K. Sinha, Liangzi Deng, Carlos de los Reyes, Banki Manmadha Rao, Maggie Paulose, Ram Neupane, Amey Apte, Vidya Kochat, Robert Vajtai, Avetik R. Harutyunyan, Ching-Wu Chu, Gelu Costin, Douglas S. Galvao, Angel A. Martí, Peter A. van Aken, Oomman K. Varghese, Chandra Sekhar Tiwary, Anantharaman Malie Madom Ramaswamy Iyer, Pulickel M. Ajayan

    With the advent of graphene, the most studied of all two-dimensional materials, many inorganic analogues have been synthesized and are being exploited for novel applications. Several approaches have been used to obtain large-grain, high-quality materials. Naturally occurring ores, for example, are the best precursors for obtaining highly ordered and large-grain atomic layers by exfoliation. Here, we demonstrate a new two-dimensional material ‘hematene’ obtained from natural iron ore hematite (α-Fe2O3), which is isolated by means of liquid exfoliation. The two-dimensional morphology of hematene is confirmed by transmission electron microscopy. Magnetic measurements together with density functional theory calculations confirm the ferromagnetic order in hematene while its parent form exhibits antiferromagnetic order. When loaded on titania nanotube arrays, hematene exhibits enhanced visible light photocatalytic activity. Our study indicates that photogenerated electrons can be transferred from hematene to titania despite a band alignment unfavourable for charge transfer.

    更新日期:2018-05-08
  • Band structure engineering of 2D materials using patterned dielectric superlattices
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-07
    Carlos Forsythe, Xiaodong Zhou, Kenji Watanabe, Takashi Taniguchi, Abhay Pasupathy, Pilkyung Moon, Mikito Koshino, Philip Kim, Cory R. Dean

    The ability to manipulate electrons in two-dimensional materials with external electric fields provides a route to synthetic band engineering. By imposing artificially designed and spatially periodic superlattice potentials, electronic properties can be further altered beyond the constraints of naturally occurring atomic crystals1,2,3,4,5. Here, we report a new approach to fabricate high-mobility superlattice devices by integrating surface dielectric patterning with atomically thin van der Waals materials. By separating the device assembly and superlattice fabrication processes, we address the intractable trade-off between device processing and mobility degradation that constrains superlattice engineering in conventional systems. The improved electrostatics of atomically thin materials allows smaller wavelength superlattice patterns relative to previous demonstrations. Moreover, we observe the formation of replica Dirac cones in ballistic graphene devices with sub-40 nm wavelength superlattices and report fractal Hofstadter spectra6,7,8 under large magnetic fields from superlattices with designed lattice symmetries that differ from that of the host crystal. Our results establish a robust and versatile technique for band structure engineering of graphene and related van der Waals materials with dynamic tunability.

    更新日期:2018-05-08
  • Exploring the speed limit of toehold exchange with a cartwheeling DNA acrobat
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-07
    Jieming Li, Alexander Johnson-Buck, Yuhe Renee Yang, William M. Shih, Hao Yan, Nils G. Walter

    Dynamic DNA nanotechnology has yielded nontrivial autonomous behaviours such as stimulus-guided locomotion, computation and programmable molecular assembly. Despite these successes, DNA-based nanomachines suffer from slow kinetics, requiring several minutes or longer to carry out a handful of operations. Here, we pursue the speed limit of an important class of reactions in DNA nanotechnology—toehold exchange—through the single-molecule optimization of a novel class of DNA walker that undergoes cartwheeling movements over a field of complementary oligonucleotides. After optimizing this DNA ‘acrobat’ for rapid movement, we measure a stepping rate constant approaching 1 s−1, which is 10- to 100-fold faster than prior DNA walkers. Finally, we use single-particle tracking to demonstrate movement of the walker over hundreds of nanometres within 10 min, in quantitative agreement with predictions from stepping kinetics. These results suggest that substantial improvements in the operating rates of broad classes of DNA nanomachines utilizing strand displacement are possible.

    更新日期:2018-05-08
  • Controlling magnetism in 2D CrI3 by electrostatic doping
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-07
    Shengwei Jiang, Lizhong Li, Zefang Wang, Kin Fai Mak, Jie Shan

    The atomic thickness of two-dimensional materials provides a unique opportunity to control their electrical1 and optical2 properties as well as to drive the electronic phase transitions3 by electrostatic doping. The discovery of two-dimensional magnetic materials4,5,6,7,8,9,10 has opened up the prospect of the electrical control of magnetism and the realization of new functional devices11. A recent experiment based on the linear magneto-electric effect has demonstrated control of the magnetic order in bilayer CrI3 by electric fields12. However, this approach is limited to non-centrosymmetric materials11,13,14,15,16 magnetically biased near the antiferromagnet–ferromagnet transition. Here, we demonstrate control of the magnetic properties of both monolayer and bilayer CrI3 by electrostatic doping using CrI3–graphene vertical heterostructures. In monolayer CrI3, doping significantly modifies the saturation magnetization, coercive force and Curie temperature, showing strengthened/weakened magnetic order with hole/electron doping. Remarkably, in bilayer CrI3, the electron doping above ~2.5 × 1013 cm−2 induces a transition from an antiferromagnetic to a ferromagnetic ground state in the absence of a magnetic field. The result reveals a strongly doping-dependent interlayer exchange coupling, which enables robust switching of magnetization in bilayer CrI3 by small gate voltages.

    更新日期:2018-05-08
  • A critical evaluation of nanopesticides and nanofertilizers against their conventional analogues
    Nat. Nanotech. (IF 37.49) Pub Date : 2018-05-07
    Melanie Kah, Rai Singh Kookana, Alexander Gogos, Thomas Daniel Bucheli

    Among a wide range of possible applications of nanotechnology in agriculture, there has been a particular interest in developing novel nanoagrochemicals. While some concerns have been expressed regarding altered risk profile of the new products, many foresee a great potential to support the necessary increase in global food production in a sustainable way. A critical evaluation of nanoagrochemicals against conventional analogues is essential to assess the associated benefits and risks. In this assessment, recent literature was critically analysed to determine the extent to which nanoagrochemicals differ from conventional products. Our analysis was based on 78 published papers and shows that median gain in efficacy relative to conventional products is about 20–30%. Environmental fate of agrochemicals can be altered by nanoformulations, but changes may not necessarily translate in a reduction of the environmental impact. Many studies lacked nano-specific quality assurance and adequate controls. Currently, there is no comprehensive study in the literature that evaluates efficacy and environmental impact of nanoagrochemicals under field conditions. This is a crucial knowledge gap and more work will thus be necessary for a sound evaluation of the benefits and new risks that nanoagrochemicals represent relative to existing products.

    更新日期:2018-05-08
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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